Fats, tumours and survival: Investigating the prognostic association of fatty acid oxidation in breast cancer

Over the past 15 years, a number of prognostic and treatment predictive signatures for breast cancer have been reported and utilised in the clinic. These signatures, for most part, are dominated by genes that reflect tumour proliferation, and provide limited insight into the biological pathways that drive tumour growth. Large gene expression datasets from primary tumours and well annotated clinical follow-up data have the potential to identify pathways correlated with treatment response and outcome. Rewiring of cellular metabolism is vital to meet the proliferative demands of tumours. To date, very little is known about how tumour metabolism influences patient outcome. This study sought to identify and characterise the metabolic features of tumours which associate with survival in breast cancer patients. Cox regression and gene set enrichment analyses were performed on gene expression data from 973 breast cancer patients. High expression of a signature comprised of 19 genes involved in fatty acid oxidation (FAO) was correlated with better disease-specific survival. The prognostic performance of this signature was validated using independent datasets from breast and several other cancer types. Analysis of the FAO signature in tumour-normal gene expression data revealed decreased expression in tumours compared to normal counterparts, which was exacerbated in advanced disease, compared to primary tumour tissues. The FAO signature was downregulated in various models of EMT induction in cell and organoid systems, independently of proliferation. Additionally, activation of MAPK and Wnt signalling pathways were observed to downregulate expression of the FAO signature in gene expression datasets from in vitro and in vivo systems. Overexpression of CPT1A in MDA-MB231 breast cancer cells decreased the proliferation and wound healing rates. No significant differences were observed in transwell migration rates, or colony formation in soft agar between basal and CPT1A overexpressing cells. MCF7 breast cancer cells with CPT1A knockdown did not alter proliferation rates or colony formation in soft agar, compared to basal expression control. Modulation of CPT1A expression did not alter oxygen consumption in response to exogenous palmitate. Transcriptome analysis suggested that transcriptional activity of EMT, MAPK and Wnt pathways was increased in MCF7 cells with CPT1A knockdown suggests a trend towards increased transcriptional activity of these pathways in this cell system. In summary, this work suggests that cancer cell proliferation and migration processes decreases the FAO signature expression, which is associated with poor patient prognosis. Alterations in the rate-limiting enzyme of this pathway alters proliferation and migration rates in MDA-MB231 cells, and increases expression of genes corresponding to key oncogenic pathways in MCF7 cells. These findings warrant further investigation of this pathway in breast and other cancer cell types. Understanding of how FAO affects tumour biology could help advance therapies that modulate this pathway

Fats, tumours and survival: Investigating the prognostic association of fatty acid oxidation in breast cancer

Over the past 15 years, a number of prognostic and treatment predictive signatures for breast cancer have been reported and utilised in the clinic. These signatures, for most part, are dominated by genes that reflect tumour proliferation, and provide limited insight into the biological pathways that drive tumour growth. Large gene expression datasets from primary tumours and well annotated clinical follow-up data have the potential to identify pathways correlated with treatment response and outcome. Rewiring of cellular metabolism is vital to meet the proliferative demands of tumours. To date, very little is known about how tumour metabolism influences patient outcome. This study sought to identify and characterise the metabolic features of tumours which associate with survival in breast cancer patients. Cox regression and gene set enrichment analyses were performed on gene expression data from 973 breast cancer patients. High expression of a signature comprised of 19 genes involved in fatty acid oxidation (FAO) was correlated with better disease-specific survival. The prognostic performance of this signature was validated using independent datasets from breast and several other cancer types. Analysis of the FAO signature in tumour-normal gene expression data revealed decreased expression in tumours compared to normal counterparts, which was exacerbated in advanced disease, compared to primary tumour tissues. The FAO signature was downregulated in various models of EMT induction in cell and organoid systems, independently of proliferation. Additionally, activation of MAPK and Wnt signalling pathways were observed to downregulate expression of the FAO signature in gene expression datasets from in vitro and in vivo systems. Overexpression of CPT1A in MDA-MB231 breast cancer cells decreased the proliferation and wound healing rates. No significant differences were observed in transwell migration rates, or colony formation in soft agar between basal and CPT1A overexpressing cells. MCF7 breast cancer cells with CPT1A knockdown did not alter proliferation rates or colony formation in soft agar, compared to basal expression control. Modulation of CPT1A expression did not alter oxygen consumption in response to exogenous palmitate. Transcriptome analysis suggested that transcriptional activity of EMT, MAPK and Wnt pathways was increased in MCF7 cells with CPT1A knockdown suggests a trend towards increased transcriptional activity of these pathways in this cell system. In summary, this work suggests that cancer cell proliferation and migration processes decreases the FAO signature expression, which is associated with poor patient prognosis. Alterations in the rate-limiting enzyme of this pathway alters proliferation and migration rates in MDA-MB231 cells, and increases expression of genes corresponding to key oncogenic pathways in MCF7 cells. These findings warrant further investigation of this pathway in breast and other cancer cell types. Understanding of how FAO affects tumour biology could help advance therapies that modulate this pathway